EUV-PHOKA - Multi-channel monitor for measurements of transmittance of solar EUV-emission in the thermosphere

EUV-Phoka is intended to record solar soft X-ray and EUV radiation (1 - 130 nm) in six spectral windows. Each channel includes a silicon photodiode AX UV-100 with a collimator and an appropriate spectral filter, a preamplifier and a voltage-to-frequency converter. The precession of the measurement by the diode is better than 1%, and the absolute accuracy is about 10 %. - In addition, there is a channel to record the visual light. EUV-Phoka will be installed onboard the "PHOTON" satellite, which is oriented to the Sun. Oc cultation measurements will provide a data base to derive parameters such a s neutral temperature and density profiles for theoretical and empirical mo deling of the thermosphere and ionosphere in the altitude range from 100 to 450 km. [GRAPHICS] During the last years many space experiments such as the YOHKOH, CORONAS-1 and SOHO missions collected solar XUV/EUV data with high spatial and spectr al resolutions whereas the primary goal of EUV-Phoka is defined to determin e the spectral irradiance from the total solar disk within the broadest wav elength range by the group of PHOTON experiments [1,2]. (C) 2000 Elsevier S cience Ltd. All rights reserved.